1. Field of the Invention
This invention relates to a centralizing support mechanism for the tubing portion of a coating lance to cooperate with the interior bore of a conduit to be coated by axial movement of the coating lance through such conduit.
2. Description of the Prior Art
It has been common practice in the coating of drill pipe for oil, gas or water wells and similar conduits to effect the coating by pulling through the pipe a coating lance, comprising a fluid slinging disc driven by an air motor and mounted on the end of a tube which functions not only to support the coating lance and move it through the bore of the pipe, but also to supply pressured fluid for coating and air to drive the fluid operated motor. Coating fluid is radially discharged by the slinging disc to form a uniform coating on the interior walls of the pipe as the coating lance is moved axially through the pipe.
Obviously, the consistency of the depth of coating applied to the interior pipe surface is a function of the location of the axis of the rotating sling relative to the axis of the interior pipe bore. Prior art devices have utilized centralizers in the form of wooden support skids which rested on and slid along the bottom surface of the pipe bore surface to be coated. This apparatus has not proven to be reliable in that the skid is subject to bouncing and tends to move within the pipe to one side or the other of the tubing bore and thus vary the alignment of the sling axis with the axis of the pipe bore. Furthermore, it is well known that each length of pipe has definite variations in internal bore diameter and the prior art centralizing device did not provide any mechanism for compensating for such variations.
There is, therefore, a need for a centralizing device for insuring that a coating lance will accurately maintain its coaxial alignment with the bore of a pipe to be coated as the lance is pulled through such pipe.